Tanning and bleaching leather with a sulfoaromaticmelamine-formaldehyde resin



Patented June 3, 195?;

TANNING AND BLEAOHING LEATHER WITH A SULFOAROMATICMELAMINE-FORMAL-DEHYDE RESIN Jack T. Thurston, Riverside, and Pierrepont Adams,Glenbrook, Conn., assignors to American Cyanamid Company, New York, N.Y., a

corporation of Maine No Drawing. Application August 12, 1949,

, Serial No. 110,022

' Claims.

This invention relates to the treatment of skins and/or hides and moreparticularly, to processes for bleaching or whitening chrome tannedleather and to the leather products obtained by such processes.

It is an object of the present invention to produce white leather.

It is another object of the present invention to provide a process forbleaching chrome tanned leather. I

Another object of the present invention is the provision of new andimproved bleaching agents for chrome tanned leather.

A further object of the present invention is the provision of new andimproved agents for tanning hides and. skins to produce white leather.

The above and other objects may be attained by treating skins and/orhides or leather with a water-soluble aldehyde condensation product of a.sulfonated aromatic hydrocarbon-substituted melamine or an alkali metalor ammonium salt thereof.

The invention will be described in greater detail in conjunction withthe following examples in which proportions are given in parts byweight. The examples are merely illustrative, and it is not intendedthat the scope of the invention should be limited to the details thereinset forth.

Example 1 254 parts (0.9 mol) of p-sulfophenylmelamine 360 parts (0.9mol) of sodium hydroxide,

aqueous 219 parts (2.7 mols) of formaldehyde, 37%

aqueous The above ingredients are placed together in a suitable vesselequipped with means for reflux. The reaction mixture is heated andrefluxed for l-3 hours. The product is cooled and filtered.

Example 2 A 30.4 parts (0.1 mol) of sodium salt of p-sulfophenylmelamine16.2 parts (0.2 mol) of formaldehyde, 37%

aqueous 150 parts of water Example 3 37.4 parts (0.12 mol) of sodiumsalt of p-sulfophenylmelamine 2 10.0 parts (0.12 mol) of formaldehyde,37%

aqueous 181 parts of water The procedure of Example 2 is followedexceptthat the reaction mixture is refluxed for only one hour.

Example 4 The procedure of Example 215 followed except that the reactionmixture is refluxed for only one hour and the product is clarified bypassing it through a centrifuge. I

Example 5 1350 parts (3.8 mols) of sodium salt of p-sulfophenylmelamine,85 purity 452.0 parts (5.6 mols) of formaldehyde, 37%

aqueous 5198 parts of water The above ingredients are mixed together ina suitable vessel and heated at reflux for one hour.

After cooling for one hour, the reaction product is clarified by passingit through a centrifuge.

Example 6 10.9 parts (0.025 mol) of the mono-sodium salt of4,8-disulfo-alpha-naphthylmelamine 6.1 parts (0.075 mol) offormaldehyde, 37%

aqueous 73.6 parts of water An aqueous solution of the sulfon'aphthylmelamine is heated with excess alkali, the'excess alkali is neutralizedwith hydrochloric acid and the solution, with triethanolamine.

Ea'ample 7 10.9 parts (0.025 mol) ofthe mono-sodium salt of6,8-disulfo-beta-naphthylmelamine 6.1 parts (0.075 mol) of formaldehyde,37%

aqueous 73.6 parts of water The procedure of Example 6 is followed, andthe slightly hazy solution obtained is filtered Formalde hyde is thenintroduced and the ingredients are mixed together in a suitable vesseland heated at Y warm. The filtered solution, which is precipitated by mt re o alt end is Pis -d a a tanning and r bleaching agent for leather.

Example 8 13.1 parts (0.025 mol based on average molecular weight) of amixture of the mono;- and cliammonium salts of 3,6,8-trisulfoialpflflfll ph thylmelamine 6.1 parts (0.075 mol) of formaldehyde. 37%

aqueous r 1 71.5 parts of water The above ingredients are placed in asuitable vessel and heated. At the boiling .point, the

reaction mixture clears to a yellowbran'g'solu tion which is refluxedfor 1 hour and then cooled. The solution obtained has good bleachingpropi ss l ihs "Example 9 100 parts of pickled kidskin are drummed with100 parts of water containing lo'parts of sodium lqr dg- .23 par s o ther s n of Exam le e addedthe sk nis tumbled o an :hour. nd

are added- After f rther tumbl n 1. rom 12-15 hours, the tanned skin hasa pH of 2.4.

12.8 parts of borax are then added to the skin hich i d ummed $9. a h urnt 9 he skin is' now'. 4.85.

kierlashed and arts?! ut Emir tes wet, it is white and well tanned. 7

Example 11 Pieces of chrome tanned side leather are by wight, basedonthe shaved weight of the stock, "or Water containing-10%"of' theresinof Example 2, 10%. of the resin of Example 3, and of the resin ofExample 1, respectively.

low by sulfonation .of phenylmelamine or it may in 00% I drumming in amedium float of water containing 3% sodium acetate for 20 rninutesat 85F. The drum is drained to a shortfioat, 20% of the resin of Example 5 isadded, and the leather is drummed for 45 minutes at 120 F. The leatheris then fat liquored and dried. A bright white l ath r su ts- Theprsulfophenylmelamine used in Example 1 and :for .the prep'aration ofits sodium salt for Examples 2 5 maybe prepared as described be- .berepared directly by condensation of sulfanilic acid and arnmonia withcyanuric chloride. We have found thatsulfanilic acid Will not condensewith melamine in the same manner as it does with urea to form thecorresponding sulionated phenyl .deriyative.

Hawa an f ,v-wlfwhe y e a ms .41 ha t? 09. 119 9 9? ahecr mslan-im pai-361 9 9i9, a&isi 9 Pa ts 9: wate A mixture of the first twoingredients is heated with stirring at about 100 C. After 1 5 minutesthe solution is pink in color and contains 0.33 mol ofsulfuric acid. Thesulfonation is'completed by stirring for an additional minutes "at about100 C. The reaction product is then cooled with ice, and the water isadded dropwise' to the' cooled sul-fonation mixture. 13.5 parts of awhite insoluble material is obtained after filtration, washing withwater and drying at 106 C. The sulfonation thus yields 69%p-suliophenylmelamine. V

The naphthylmelamines of Examples 6-8 may be prepared by" reaction ofcyanu-rio chloride with the corresponding naphth ylamine sulfonic acid.The procedure is illustrated by the follow- Theyare then washed, tackedout and dridl 1n 1 each case :wel-l bleached leather results"? Example12 I Pieces of chrome tanned side leather are shed i911}?! 11 3143 a.ahqyt 2%.??

c.2 12 s i'lilea h d $9 .0 m n tes t HQ G- 1. 9% ath ist! base 9a thshared us aht a e k f wa c nt n n 9% nd 29% r e e am le tad. 19% as .9%.nin ay i am e 1, re pectivel Thsy are hen s ed t i i q but at; areableached.

aaaa- Eatamplem V Pieces of chrome tanned leather are washed in tapwater for 1% hours and then drummed for 1 i=9. 1:597? 1 2 Weight ased.th shar d Weiht th ste s 9f Wat r cgntaia n 29 s tes ease o res cm a.They are then washed, tacked out and dr ed, The skins obtained are wellbleached. I

chrome tanned side leather isineutrailz'ea by mg detailed preparation.

A solution of {(4 parts (0.4 'mol) of cyanuric chloride in 127 parts ofhot acetoneis'poured into a mixtureo'f 400 parts of ice and 400 parts ofwater. To this are added 12-2 parts (0.4 mol) of 1-naphthy1amine-4,8disulfonic acid as a slurin an Part 9 wa er n 60 Part or 19 dium h naiq.s l ti a The mi ture s stirred at 15 -20" 0. for 1.5 hours. parts of aeais ammpni ar hen dde and t e reaction is allowed to continue foranother 1.? hours, the temperature rising to 33 C. 50 parts r Of theammonia are then added, and the reaction mixture is heated under refluxfor 1. urs an fi ter d hot. r

292 parts of 10% hydrochloric acid are added to the filtrate and themixture is allowed to cool. The solution is reduced toabout one fifthits um y ev p at o an t en c oled and n1; tered. The solid isrecrystallized iron a small amoun o We??? aml is at 10 aromatichydrocarbon-substituted melamines described in the aforegoing examplesand the accompanying description have the formula where R is an aromatichydrocarbon radical and X is selected from the group consisting ofhydrogen, alkali metal and' ammonium, and 1 1., is an integer from 1 to3.

Similarly, formaldehyde-yielding materials such as paraformaldehyde andhexamethylenetetramine may be substituted for the formaldehyde of theexamples as may other 'aldehydes including acetaldehyde, paraldehyde,furfural, and the like. I a I We have found that the melamine derivativeor salt thereof and formaldehyde should be-condensed in molar ratios offrom about 1:1 to about 1:5, respectively. p 1

' The condensation of formaldehyde with the melamine derivative maybecarried out' at pI-Is varying from about 3.5 to 9.5 without effectingthe bleaching ability of the product. We prefer carrying out thereaction at pHs of from about 6 to 9.

The formaldehyde and melamine derivative are preferably condensed forperiods of time up to about an hour at reflux. Beyond that time littleadditional formaldehyde combines with the melamine derivative. At theboiling point of an aqueous solution of melamine derivative andformaldehyde the quantity of formaldehyde combining with the melaminederivative becomes constant after about one hour and even dropping thepH of the solution after this time, for example, from about 8.5 to about4.5, does not effect the amount of combined formaldehyde.

While we have set up certain limitations on the ratio of reactants, thereaction time and the l pH of reaction, the bleaching efiect of the newresinous bleaching agents appears to be independent of these variables.

The water-soluble condensation products here described areacid-sensitive. In aqueous solution they may be converted to theinsoluble or hydrophobe state by the addition of acid, with consequentprecipitation of a solid white resin. Since the chrome salts in leathertanned therewith will generate sulfuric acid when brought into contactwith water, it is possible by the process of the present invention tocapitalize on the acid-sensitivity of the condensation products on theone hand and the capacity of the chrometanned leather to generatesulfuric acid in the presence of water on the other for the bleaching orwhitening of green chrome-tanned leather.

The bleaching process of the present invention may be carried out simplyby drumming chromed leather in a watersolution of one of the describedmelamine derivative condensation products. Varying concentrations, e.g., from about 1% to about by weight of solid resin based on the shavedweight of the stock, may be used in the process and our invention is inno sense limited to the use of any particular concentration. We preferto use from about 5% to about 25% resin. on the same basis.

The formaldehyde-melamine derivative con- 6f densation products of thepresent invention may be employed alone for the whitening of chrometanned leather, or they may be employed in combination with otherbleaching agents. In such instances the leather may be first treatedwith a secondary bleaching agent and a condensation product of thepresent invention applied thereafter, the two bleaching agents may beused in conjunction with each other, or the secondary bleaching agentmay be used for after-treatingleather which has been bleached with theproducts described in the present case.

Moreover, the condensation products of the present invention may be usedas tanning agents, see Example 7, either alone or in conjunction withother tanning agents, i. e'., vegetable, mineral or synthetic.Ifthelatter, our new agents may be used for the initial tannage or forthe after-tannage.

The leather products obtained by'the process of the present inventionand having incorporated therein a formaldehyde condensation product of asulfonated aromatic-substituted melamine offer the advantage in themanufacture of white leathers of a reduced requirement of white pigmentsuch as titanium dioxide for covering the leather surface. Such bleachedleathers may also be of advantage in obtaining brighter colors indyeing.

We claim:

1. A process of tanning and bleaching which comprises treating hides andskins with an aqueous solution of a water-soluble acid-sensitivecondensation product of 1 mol of a sulfonated aromatic hydrocarbonsubstituted melamine having the formula wherein R, is an aromatichydrocarbon radical, X is selected from the group consisting ofhydrogen, alkali metal and ammonium, and n is an integer from 1 to 3with about 1 to about 5 mols of formaldehyde.

2. A process of bleaching leather which comprises treating tannedleather with an aqueous solution of a water-soluble acid-sensitivecondensation product of 1 mol of a sulfonated aromatic hydrocarbonsubstituted melamine having the formula wherein R. is an aromatichydrocarbon radical. X} is selected from the group consisting ofhydrogen, alkali metal and ammonium, and n is an integer from 1 to 3with about 1 to about 5 mols of formaldehyde.

3. A process according to claim 2 in which the substituted melamine isp-sulfophenylmelamine.

4. A process of bleaching chrome tanned leather which comprises treatingchrome tanned leather with an aqueous solution of a water-solubleacid-sensitive condensation product of 1 .7 mol of at annotated aromatichym'ombon sub stmxtefl momma having the formula wherem "R is an arozrratic hydrocarbon X ,is selected from the sroup consisting of v drogen,alkali metal and ammonimmm'nd mis 1 emmmemm 8 wherein 2B. is anhydrocarbon raekcezl. X ,is selected the group consisting of hydrogen,alkali meta-1 and :ammomum, and in is an integer from 1 to 3 with about1 to about 5 7 mols of formaldehyde, and then with a different tanningagent.

JACK T. THURSTON. PIERREPONT ADAMS.

REFERENCES CITED The following references are of record in the file ofthis patent:

STATES PATENTS Number Name 7 Date 1 949 513 Bergmmm Feb. 20, 19342,122,133, Dohse June 28, 1-938 2.303.399 Grim New. 24, 1942 2316,3210,r Apr. 13 19413 2,328,424 .D'Jflerio Aug. 31,1943 2,353,556 Grim Jul111;, 1944 2,411,679 DiAleHe Mar. &8, 194' 2,493,495 Keller t 911. June15. 949

om REFEBEN'GES Journal 5: the American Leather Chemists Association.1944. mac 9-

1. A PROCESS OF TANNING AND BLEACHING WHICH COMPRISES TREATING HIDES ANDSKINS WITH AN AQUEOUS SOLUTION OF A WATER-SOLUBLE ACID-SENSITIVECONDENSATION PRODUCT OF 1 MOL OF A SULFONATED AROMATIC HYDROCARBONSUBSTITUTED MELAMINE HAVING THE FORMULA